Surgical stapling instruments used for applying parallel, linear rows of staples through compressed living tissue are well known in the art, and are commonly used for closure of tissue or organs prior to transection or resection, and for occlusion of organs in thoracic and abdominal plasty procedures.
One such stapler is described in U.S. Pat. No. 4,863,088. That stapler comprises a firing assembly for substantially sequentially applying a plurality of linear rows of staples which includes an anvil. The anvil comprises specially shaped surfaces that are adapted to engage and form the staples into the desired orientation during firing of the stapler. An anvil is described in published Canadian Patent application No. 1,284,551 and Australian patent application No. 589,001. Optionally, a knife may be present for cutting between the rows of applied staples.
A commercial embodiment of the above described stapler has been available under the trade designation "The ILA Stapler", catalog #3957 by Minnesota Mining and Manufacturing Company (3M), St. Paul, Minn. The use of an ILA surgical stapler is described in the publication entitled "Surgical Stapling, Gastric and Small Bowel Procedures, Volume I", ISBN 0-937433-00-4, Library of Congress Catalog Number 85-082599 available from Minnesota Mining and Manufacturing Company (3M), St. Paul, Minn., the contents of which are herein incorporated by reference.
That surgical stapler is known as a "reusable" surgical stapler. As used in this application, the phrase "reusable surgical stapler" means a surgical stapler which may not only be fired several times on the same patient (with, for example, the use of replaceable cartridges), but may also be sterilized and reused on a different patient. Such a stapler stands in opposition to what is known in the art as a "disposable surgical stapler". While a disposable surgical stapler may be reused several times on the same patient, a disposable surgical stapler is not meant to be sterilized or used on a plurality of patients.
Because disposable and reusable staplers may be used to fire a plurality of cartridges, both disposable and reusable surgical staplers may have a replaceable anvil. As used in this application, the phrase "replaceable anvil" means an anvil which may be removed from the stapler by hospital personnel, and replaced with a different, sterilized or refurbished anvil.
Typically a replaceable anvil is constructed from a biocompatible material such as stainless steel. A surface coating, such as Teflon (polytetrafluoroethylene, PTFE), may be provided on the stainless steel replaceable anvil in order to improve its friction characteristics, as the friction characteristic of an anvil is an important consideration for the proper formation of staples in tissue.
Reusable and even disposable surgical staplers encounter problems due to the tendency for the staple formation characteristics of an replaceable anvil to degrade over multiple uses. One cause of this is believed to be excessive wear of the Teflon coating resulting in the destruction of the desired friction coefficient of the anvil. Over multiple uses, some anvils will gall resulting in diminished staple formation performance of the anvil and potentially even an increased firing force. Excessive galling may result in crashed or malformed staples, clearly an undesirable result.
At least partially because of such concerns, reusable and disposable staplers have been provided with replaceable anvils to ensure proper staple formation. However, prior art disposable and reusable staplers with replaceable anvils encounter problems because some users may not recognize when an anvil is absent from the stapler. Should the stapler be fired without a properly positioned anvil, the resultant staples will be malformed, an undesirable result, particularly when an optional knife is used to cut between the applied rows of staples. If an anvilless stapler is clamped on tissue to be stapled, the compressive forces created by the stapler subject the tissue to unnecessary trauma. Even if a surgeon were fortunate enough to recognize that the surgical stapler clamped on tissue lacked an anvil, precious time would be lost in unclamping the stapler, replacing the anvil, and again clamping the stapler on tissue.
Another stapling instrument used for applying linear parallel rows of staggered staples through compressed living tissue is currently available under the trade designation "The PI Stapler", catalog #3960 by Minnesota Mining and Manufacturing Company (3M), St. Paul, Minn., the use of which stapler is described in a publication entitled "Surgical Stapling, Gastric and Small Bowel Procedures, Volume I", ISBN 0-937433-00-4, Library of Congress Catalog Number 85-082599 available from Minnesota Mining and Manufacturing Company (3M), St. Paul, Minn. That stapler and a similar stapler described in EPO Application No. 514 139 are adapted for substantially simultaneously firing staples into compressed living tissue from a staple filled cartridge. The PI-type staplers have anvil and jaw portions, an alignment pin, a cartridge holder including a removable cartridge and a handle lever.
The stapler described in EPO Application No. 514 139 includes a device for preventing the jaws from clamping on tissue unless an alignment pin is properly positioned. This device, however, is not dependent upon whether an anvil is present. That device would not necessarily prevent the clamping of the jaws on tissue if the stapler were completely free of an anvil.
Other surgical stapler lockout devices are described in PCT WO/92/10976, U.S. Pat. Nos. 4,892,244; 4,955,959; 5,031,814; and 5,106,008; and published European Patent Application No.'s 489,436 and 537 572. However, none of those devices interact or are cooperable with a replaceable anvil as set forth in the present invention.